Fire-resistant materials are important in the fabrication of many building materials like doors, wall components, ceiling components, roof components, etc. In the event of a fire, fire resistant products protect the integrity of the building and its components for longer periods of time giving occupants longer to escape and giving firemen longer to get to strategic points to rescue people and to fight the fire. Of secondary importance is the reduced damage to contents of the buildings. Fire-resistance relates to the maximum temperature a material can endure without burning through or collapsing (loosing its integrity) or the time it takes at a certain high temperatures to burn through, collapse or otherwise destroy the integrity of a component. Codes have been established for many products which set forth high temperature performance they must meet to be considered fire rated or fire-resistant. Fire-resistance is thus distinguished from fire retardency which is the ability of a material or component to withstand high temperature and time without catching on fire and burning.
Glass fibers and products made therefrom like insulation blankets and boards, woven fabrics and nonwoven mats are widely used in building products. Most homes and commercial and industrial buildings are thermally insulated with fiber glass insulation products in the form of bats, blankets, higher density boards, ceiling tile, etc. Most asphalt shingles have a fiber glass nonwoven mat as a base. Glass fiber is used in gypsum wall board to make the board fireproof. There are numerous other building products that use glass fiber and there are other opportunities if the glass fiber had a higher use temperature.
The majority of glass fiber products used in building products today are either sodium borosilicate glass having a softening point of as low as about 1290 degrees F. or E type borosilicate glass having a softening point as low as about 1529 degrees F. The softening points of these fiber products will vary some from manufacturer to manufacturer since slightly different glass compositions are used, but will be within a narrow range of about 10-40 degrees F. While more refractory glass fibers are known, like magnesia aluminosilicate S glass, the high cost of these types of fiber are prohibitive for all but a very few specialty building products.
As disclosed in U.S. Pat. No. 5,284,700, the disclosure of which is hereby incorporated by reference, it is known to treat or coat glass fibers with a phosphate containing compound to improve its fire-resistance. The theory was that the phosphate compound either broke down at high temperature to form phosphoric acid which combined with silica in the glass to form a silicate phosphate ceramic coating on or near the glass fiber or via formation of a high melting temperature phosphate surface coating or layer. It was also taught in this patent to add the phosphate to a binder solution normally used to coat the fibers and bond them together as a way of applying the phosphate compounds. Finally, this patent also taught a fire-resistant laminated fiber glass insulation product in which a nonwoven fiber glass mat, treated in accordance with that invention to make it fire-resistant, was laminated on each surface to a layer of fiber glass insulation blanket to make a fire-resistant insulation product.
U.S. Pat. No. 4,145,371 by Tohyama et al discloses a flame-retardant textile fiber consisting of PVA and an amino resin. The amino resin is a condensation product of formaldehyde with melamine and other amino compounds selected from urea, dicyandiamide and benzogranamine. The use of phosphorous additives is suggested to enhance the flame-retardant characteristics of the fiber. The addition of dicyandiamide was found to improve the color fastness of the fiber.
It is also known to use relatively large amounts of a phosphorus containing compound to produce a fire retardant condensate as taught by Goulding et al in U.S. Pat. No. 4,195,139. There a melamine-aldehyde is reacted with a relatively large amount of at least one oxyacid of phosphorous in a condensation reaction to form the fire retardant, the inorganic phosphorus compound being added in sufficient amounts that phosphorous is present in the resulting condensation product in the ratio of 0.4-1.7 moles of phosphorus for every mole of melamine.
After making the present invention and doing literature search to try to find out why and how the invention works, it was discovered that it is known to react urea and condensation products of urea with boric acid and boron oxide to produce boron nitride, as described by Podsiadlo and Gontarz in the POLISH JOURNAL OF CHEMISTRY, 58, 3 (1984) and Podsiadlo and Gorski in the POLISH JOURNAL OF CHEMISTRY, 58, 13, (1984). It is also know to react calcium, strontium and barium cyanamides with boric acids and boron oxide to form a boron nitride containing material as described by Podsialdlo and Orzel in the POLISH JOURNAL OF CHEMISTRY, 58, 323 (1984). However, each of these three articles, which are hereby incorporated by reference, reported only on the nature of the reactions and neither of the articles involved or suggested treating glass fibers, or other substrates, or making fire resistant glass fibers and glass fiber products using these reactions. Therefore, it is not known yet whether boron nitride is in fact being formed as a refractory sheath around the fibers making the fibers more fire resistant, but it is believed by the inventor that this is why the invention works.
It is known in the art to add boric acid to phenol-formaldehyde resins to obtain reactions with the resin to achieve stronger bonds and to allow the resin to withstand higher temperatures before breaking down or decomposing. Thus, as disclosed in U.S. Pat. No. 4,480,068 (Santos), U.S. Pat. No. 4,176,105 (Miedaner) discloses that the temperature resistance of binders can be increased by the addition of boron compounds to modified phenolic resins, but attempts to employ borates in sufficient quantities needed to give the binder improved thermal resistance frequently result in resins having poor storage stability and poor tensile strength. The reason given was that the addition of larger amounts of boric acid disrupts, accelerates, the cure of the binder resulting in precure before the product the binder is in has been collected or molded, reducing the final strength of the bonds formed in the final cure. Santos taught adding an amide such as dicyandiamide and a pre-mixed boric acid-hydroxyl component to a urea modified phenol formaldehyde resin to permit the cured resin to withstand higher temperatures, but only up to 455 degrees C (851 deg. F.). Santos only showed one binder containing over four percent boric acid and this sample showed reduced dry tensile and very poor wet tensile strengths. Santos did not teach or suggest that the binder of his invention would be fire resistant or that it would allow glass fiber products to withstand temperatures in excess of the softening or melting points of the glass fibers.
U.S. Pat. No. 3,218,279 (Stalego) taught punk resistant borated alkyd resin binders for glass fiber products in which a relatively small amount of phenol formaldehyde resin was also present, but the amounts of nitrogen compound and boron compounds in the binder were relatively low. There was no suggestion in this patent that the binder would protect the fibers in a fire or at temperatures above the softening and melting points of the glass fibers.
U.S. Pat. No. 2,990,307 taught using boric acid with phenol formaldehyde/melamine resins to bond glass fibers to give the product increased punk resistance, but only 2.5 percent boric acid is used and the product was only heated to 600 degrees F. There was no suggestion that the binder would protect the fibers in a fire or at temperatures above the softening and melting points of the glass fibers.
U.S. Pat. No. 4,095,010 taught using 0.5-2 percent boric acid as a cure accelerator, because of its low pH, in a phenolic resole resin fiber glass binder containing 5-15 percent urea or melamine. There was no suggestion that the binder would protect the fibers in a fire or at temperatures above the softening and melting points of the glass fibers.
U.S. Pat. No. 4,529,467 taught a thick, paste-like, epoxy resin based fire protecting intumescent composition containing a few percent of melamine and enough boric acid to produce a boron content of 0.1-10 percent. The purpose of the melamine was to produce a gas to cause the mastic to expand when exposed to fire. The composition could contain from 1-50 percent, based on the weight of the epoxy resin, curing agent and melamine, of fibrous reinforcements like chopped glass fiber to hold the composition together when it was heated by a fire to form a char. This composition also required the presence of zinc and phosphorous. A fiber glass mesh membrane could also be embedded in the mastic to hold the charred mastic together and on or around a steel member it was intended to protect. There was no suggestion that the mastic would protect the fibers at temperatures above the softening and melting points of the glass fibers and the highest temperature used for testing the compositions was 1000 degrees F (538 degrees C.).